Centrifugal pumps



1963 E. DUNCOMBE ET AL 3,074,343

CENTRIFUGAL PUMPS Filed Feb. 10, 1960 2 Sheets-Sheet 2 WAVAQ NW MIMNTORS EDWARD DU'NCOME HAROLD PUGH iinited dtates 3,074,348 CENTRKFUGALPUMPS Edward Duncombe, Great Saughall, Chester, and Harold Pugh, Wirral,England, assignors to United Kingdom Atomic Energy Authority, London,England Filed Feb. 10, 1960, Ser. No. 7,904 Claims priority, applicationGreat Britain Feb. 17, 1959 1 Ciaim. (Cl. 10387) This invention relatesto apparatus using centrifugal pumps for the sampling of radio-activeliquids.

In plants handling radio-active liquids it is generally desirable toprovide access points from which samples of the liquids can be taken forroutine analysis purposes. These access points may take the form ofsampling troughs in the liquid flow stream, but in order thatmaintenance required at the troughs can be carried out there has to beprovision for by-passing the troughs, which involves additional plantitself requiring maintenance. Alternatively, the access points may takethe form of sampling troughs removed from the liquid flow stream. Thereis then the need to deliver the liquid to the sampling troughs from theliquid flow stream using apparatus requiring as little maintenance aspossible. It is an object of the invention to provide such apparatus.

The invention, in its application to the sampling of radio-activeliquors, resides in apparatus comprising biological shielding havinginside the shielding a pipe for radioactive liquors and outside theshielding a pipe for radio-active liquors drawn off from said pipeinside the shielding, a centrifugal pump having its inlet communicatingwith the pipe inside the shielding and its outlet connected with anoutlet pipe coupled to the pipe outside the shielding, the apparatushaving the characterising features that, first, the pump is containedwithin a casing extending from outside said shielding to be integralwith the pipe inside the shielding, second the pump is removable fromsaid casing through an aperture accessible from outside said shielding,third, the pump is provided with air lubricated bearings and driven byan air turbine and fourth, the outlet pipe and pipes feeding thebearings and turbine are contained within said casing to pass throughthe shielding.

By way of example, embodiments of the invention will now be describedwith reference to the accompanying drawings wherein FIG. 1 is asectional elevation and FIG. 2 is a partly diagrammatic sectionalelevation.

Referring to FIG. 1, a centrifugal pump 40 generally of stainless steelconstruction comprises a shaft 50 carrying an impeller 51, and isarranged so that the shaft 50 can be supported on an air lubricatedthrust bearing 54, centralized on spaced air lubricated journal bearings52 and 53, and rotated by an air powered turbine rotor 55.

The pump has a casing 56 comprising a circular section tube 57 to whichis welded a flanged ring plate 58. An impeller base plate 59 is securedto the plate 58 by screws 60, the plates 58, 59 forming a housing forthe impeller 51. The plate 59 has an impeller inlet port 61 and theplate 58 has an impeller outlet port 62 connected to an outlet pipe 63.The tube 57 has a ring of holes 64 and a ring of vent holes 65.

The casing 56 further comprises a circular section tube 66, the tubes57, 66 being connected by a welded connecting ring 67. A bearing sleeve68 is close-fitting in the ring 67 and has a flanged end 69 secured byscrews 70 to a flanged mounting ring 71 welded to the tube 66. Thebearing 52 comprises a stepped portion of the sleeve 68, the shaft 50having a complementary stepped portion 72. The bearing 52 has a ring oforifice jets 73 (one of which is shown) equi-spaced around the steppedportion 72 of the shaft 50. Similarly the bearing 53 comprises 3,074,348Patented Jan. 22 1963 iee a stepped portion of the sleeve 68, the shaft50 having a complementary stepped portion 74. The bearing 53 has a ringof orifice jets 75 (one of which is shown) equispaced around the steppedportion 74 of the shaft 50. The bearing 54 comprises a ring of orificejets 76 (one of which is shown) equi-spaced around the flanged end 69 ofthe sleeve 68, and the shaft 50 has an integral annular thrust plate 77.The bearing surfaces of the bearings 52, 53, 54, of the stepped portions72, 74 and of the thrust plate 77 are of a size and surface finish suchas to maintain air lubrication.

The turbine rotor 55 comprises a first rotor plate 78 having a ring ofcurved blades 79 and a second rotor plate 80 having a ring of similarlycurved blades 81, the plates 78, 80 being secured to the plate 77 byscrews 82. A deflector unit 83 located in a sleeve 84 welded to the ring71 has a ring of curved deflector blades 85, the blades 85 being curvedin the opposite direction to the blades 79, 81. The plate 77 has anannular stepped portion 86 and a curved peripheral face 87, and thesleeve 84 has vent holes 88. A sleeve 89 vertically movable in an axialbore 90 in the shaft 50 houses a spring 91. The lower end of the spring91 is attached to a pin 92 located by the shaft 50 and the upper end ofthe spring-91 is attached to a pin 93 each end of which is located in anotch 94 in the sleeve 89. The plate 78 has three equi-spaced pockets 95(one of which is shown) each housing a ball 96 and having an associatedinclined track 97. The sleeve 89 has secured to it three equi-spacedarms 98 (one of which is shown) each held by the force of the spring 91on one of the balls 96. The sleeve 89 also has secured to it a cap 99.

The upper end of the pump 40 is enclosed by av cover plate 100 securedby screws 101 to a flanged ring 102 welded to the sleeve 84. The parts57, 58, 59, 66, 67, 71, 84, 100 and 102 form the casing 56. The coverplate 100 has a recess 103 into which extends a striker 104 of a closuremember 105. The member 105 is movable vertically in a bore in the coverplate 100, the bore having a step 106 to position the member 105, andthe bore communicates with a similar bore of air inlet pipe 107 weldedto the cover plate 100. The pipe 107 and cover plate 100 are arranged toprovide an inlet 108 to passageways 109 communicating with an annularspace 110 bounded by the cover plate 100. Passageways 111 extend throughthe cover plate 100 from the annular space 110 to the top of the blades79 of the rotor plate 78.

The jets 73, 75, 76 have a common annular space 112 bounded by thecasing 56 and the sleeve 68, and an inlet pipe 113 communicates with thespace 112 via a stub pipe 114 welded to the tube 66. Passageways 115(one of which is shown) in the sleeve 68 connect annular space 116between the stepped portions 72, 74 of the shaft 50 with annular space117 between the sleeve 68 and the plate 77. Passageways 118 (one ofwhich is shown) through the flanged end 69 of the sleeve 68 extend fromthe annular space 117 to the region of the vent holes 88 in the sleeve84.

The pump 40 is supported from a pipe 119, a mounting ring 120 welded tothe pipe 119 being secured to to the pipe 123 so as to be integral withit. The impeller inlet port 61 communicates with the pipe 123 and thelevel of the radioactive liquors in the casing 122 is indicated by line124. The casing 122 hasa flushing water inlet pipe 125 connected to aring pipe 126 having holes 127. The casing 122 also has a support base128 mounted on a floor 129.

FIG. 2 in which like parts to those shown in FIG. 1

are indicated by the same reference numerals, shows apparatus comprisinga concrete biological shield 139 with the pipe 123 inside the shield 130and a pipe 131 outside the shield 130 for radioactive liquors drawn offfrom the pipe 123. r The pump outlet pipe 63 is coupled to the pipe 131by a pipe coupling 132. The casing 122 for the pump '40 extends from theinside to the outside of the shielding 13%) through an aperture 133; Theshielding 130 has shielding walls 134, 135 supporting a removable topshield plug 136 giving access to space 137 into which the casing 122extends. The pipe 119 extends upwardly in the casing 122 from the pump40 and has an upper end flange 13% mounted on an upper end flange 139 onthe casing 122, the casing 122 being closed at its uper end by a coverplate 140 secured to the flanges .138, 1 39. The pipes 63, 107, 113extend upwardly in the pipe 119 from the pump 40 and are sealed to thecover plate 140 in passage therethrough. The pipes 107, 113 are coupledto pipes 141, 142 by pipe couplings 143, 144 respectively. The pipes131, 141, 142 pass through an aperture 145 in the shielding wall 134,the pipe 131 connecting to a sampling trough in the form "of a tank 146.The tank 146 is housed in a shielded space 147 having a removable topshielding plug 148, and has a cover 149 and a support base 156 mountedon the shielding 130. The pipe 141 is connected to a turbine air'main151 and the pipe 142 is connected to a bearing air main 152, the mains151, 152 passing outwardly through the shielding. The cover plate 140has an exhaust pipe 153 connected to a silencer 154 having an outletpipe 155 passing out through the shielding. The pipe 123 is connected toa'tank 156 having a cover 157 and support legs 158. mounted on a floor'159. The liquor level in the tank 156 is indicated by dotted line 16%.In one application, the tank 156 contains highly radioactive aqueousraffinate from mixer settler apparatus using tributyl phosphate andwater for the separation of uranium and fission product mixtures.obtained from irradiated nuclear reactor fuel elements. The aqueousraflinate flows from the tank 156 through the pipe 123 to be stored, andperiodic analysis is carried out of the aqueous ralfinate going tostorage. To this end the pump '40 is used to periodically deliversamples of the aqueous raflinate from the casing 122 to the tank 146from which further samples may be taken by access to the space 147through the plug 148. The operation of the apparatus is now describedwith particular reference to the operation of the pump 40.

The pump 40 is operated when required by supplying compressed air firstto the jets 73, 75, 76 and then to the rotor 55. The air is fed to thejets 73, 75, 76 via the main .152, the pipe 142, the inlet pipe 113, thepipe 114 and the space 112. The air fed to the jets 76 impinges on thethrust plate 77 to provide support for the shaft 50 and to provide anair lubricating film between the flanged end 69 of the sleeve 68 and thethrust'plate 77. The air fed to the jets 73, .75 impinges-on the steppedportions 72, 74 respectively, thereby centering and stabilising theshaft 50 and providing an air lubrieating film between the bearings 52,53 and the stepped portions 72, 74 respectively.

"The air is fed to the rotor 55 via the main 151, the pipe 141, theinlet pipe 107, the inlet 198, the passage ways 109 and the annularspace 110. From the space 110 the air passes through the passageways 111to impinge on the blades 79 to rotate the shaft 50. The air then passesthrough the deflector blades 85 to impinge on the blades '81 to provideadditional rotational power to the shaft 50. The speed of the pump '40is determined bythe pressure of the compressed airfeed to the rotor 55,and it is important to supply air to the jets 4 73, 75, 76 before it issupplied to the rotor 55 thereby ensuring air lubrication between theshaft '50 and the bearings 52, 53, 54 during operation of the pump 40.

The air fed to the jets 73 flows both upwardy and downwardly over thestepped portion '72 of the shaft 59. The air flowing downwardly exhaustsfrom the pump 40 via the vent holes 65. The air flowing upwardly entersthe space 116. Similarly, the air fed to the jets 75 flows upwardly anddownwardly over the stepped portion 74 of the shaft 59. The air flowingupwardly enters the space 117 and exhausts from the pump 40 via thepassageways 118 and the vent holes 88. The air flowing downwardly entersthe space 116 whence it exhausts from the pump 4%} (together with theupwardly flowing air from the jets 73) via the passageways 115, thespace 117, the passageways 118 and the vent holes 88. The air fed to thejets 76 flows inwardly and outwardly over the flanged end 69 of thesleeve 68. The air flowing inwardly exhausts from the pump 41% via thespace 117, the passageways 118 and the vent holes 88, and the airflowing outwardly exhausts from the pump 49 via the stepped portion 86and the vent holes 88. The air fed to the rotor 55 exhausts from thepump 40 via the vent holes 38, the face 87 serving to direct the flowingair leaving the blades 31 towards the vent holes 88.

Should the pipe 123 become emptied during operation of the pump 4th, thespeed of rotation of the shaft 50 will increase until the balls 96 areurged radially out wardly by centrifugal force thereby rising up thetracks 97 and lifting the sleeve 89 (by means of the arms 98 and againstthe force of the spring 91) until the cap 99 hits the striker 1&4thereby raising the closure mem-- her and thus closing the inlet 1118and stopping the flow of air to the turbine rotor 55 until the speed ofrotation of the shaft 50 falls sufliciently for the force of the springto return the balls 96 to the pockets 95, when the closure member 105will fall and open the inlet 103.

The holes 64 ensure that the liquor being pumped covers the impeller 51.

When it is required to remove the pump -48 from the casing 122-, accessto the space 137 is achieved by removal of the plug 136. The pipecouplings 132, 143, 144 are disconnected, and the cover plate 145 isuncoupled. The pump 4% with the pipes 63, 197, 113, 119 is then readilywithdrawable through the aperture 133. The pump 4t) is spray washedbefore removal by supplying water to theholes 127 'viathe ring-pipe 126and the inlet pipe 125, and is normally withdrawn into a shieldedcontainer.

The greater part of the air fed to the bearings 52, 53, 5dand to therotor 55 exhausts from the pump 46* from the vent holes =88 above themounting ring 71. This exhaust air is well removed from the liquor levelin the casing 122 and is unimpeded in passage to the exhaust pipe 153.

The use of gas lubricated bearings and air turbine drive is advantageousin that the pump can be operated for long periods with littlemaintenance.

- The turbine drive arrangement is also advantageous in that iteliminates the problem of avoiding lubricating oil contamination of theliquid being pumped which arises when an electric motor drive is used.

The arrangement of pump and elevated sampling trough is advantageous inthat the apparatus is selfdraining through the pump when the pump isstopped.

We claim:

Apparatus comprising biological shielding having a base, upstanding sidewalls and top covers defining first and second enclosed spaces, a firstpipe disposed below said base, a casing extending from said firstenclosed space throughsaid base and connected'with said first pipe toform a fluid flowpath through the pipe and easing, a centrifugal pumpdisposed withinsaid casing below said base, said pump comprising ahousing having an inlet port and an outlet port and first and second airinlet ports, a shaft disposed within said housing, an impeller securedto one end of said shaft and a turbine rotor secured to the other end ofsaid shaft, said shaft and housing having adjacently positioned bearingsurfaces, a second pipe connected to said first air inlet port forfeeding pressurized air between said bearing surfaces to form airlubricated centralizing and support films for said shaft, a third pipeconnected to said second air inlet port for feeding pressurized air torotate said turbine rotor, said second and third pipes being containedwithin said casing to pass through said base, a fourth pipe connected tosaid outlet port and contained within said casing to pass through saidbase into said first enclosed space, a sample tank disposed Within saidsecond enclosed space, and an inlet pipe connected to said tank andconnected to said fourth pipe in said first enclosed space.

References Cited in the file of this patent UNITED STATES PATENTS 102,149,600 Guinard Mar. 7, 1939 2,864,552 Anderson Dec. 16, 19582,915,016 Weaver et a1. Dec. 1, 1959

